PROJECT SUMMARY The goal of the proposed R21 project is to build on our recent discovery of olfactory ?gating? of visual attraction in Aedes aegypti mosquitoes, and specifically to unravel how odor modulates visual processing in the mosquito brain to mediate attraction to visual objects, like features of a host. The sensory systems of mosquitoes play key roles in mediating blood-feeding behaviors, as such, sensory systems provide attractive targets for suppressing vector behaviors. Vision is a key sensory modality involved in long-range olfactory search behaviors, as well as near-host behaviors involved in landing and biting. Despite this potential importance, very little is known about vision in mosquitoes and the neural bases of these behaviors. Mosquitoes can see a host from 5-15 m, and our recent findings show that vision plays a critical role in host attraction by linking long-distance odor tracking with short-range behaviors near the host. Moreover, our recent work utilizing a new Aedes GCaMP6s mosquito line ? allowing both neuroanatomical identification and characterization ?, and generation of CRISPR dopamine receptor mutants, allowed us to determine how odor information is processed in the brain and how neuromodulators influence this processing. Now, we seek to build on these and preliminary findings that demonstrate the importance of neuromodulators in olfactory-visual integration in mosquitoes. Using behavioral assays, calcium imaging in tethered flying mosquitoes, and molecular-genetic approaches, we propose to study the visual preferences of Aedes mosquitoes, and how olfactory input modulates visual neurons. Aim 1 will allow us to characterize the visual features that attract mosquitoes and determine how long CO2 ?turns on? visual search behaviors. We also take advantage of our CRISPR Dop1 and Oct1 mutants to determine how olfactory-visual behaviors are compromised. Our preliminary results indicate these neuromodulators are critical for the olfactory gating of visual responses. In Aim 2 we will use our GCaMP6s mosquito line and two-photon microscopy to characterize how odor input modulates neurons in the optic lobe (lobula). Pharmacological and genetic interventions of Oct1 and Dop1 will allow us to further examine the importance of these pathways for sensitizing visual responses to attractive objects. While there has been extensive work on olfaction in mosquitoes, there is now increasing evidence that vision also plays a key role. Moreover, olfactory-visual integration is important in diverse insect vectors, including tsetse flies and kissing bugs. We suggest that our proposed experiments may provide a basic framework for understanding how these cues influence behavior and sensory processing. Moreover, results from this work can provide new information for utilizing additional visual cues in mosquito traps, as well as providing motivation for the identification of molecular targets to cripple visual-olfactory behaviors.